Punching configuration



A ril 7, 1970 w. E. THOMAS 7 PUNCHING CONFIGURATION 7 Filed no). 29, 1967 I N VEN TOR.

'TTORNEYS United States Patent 3,504,588 PUNCHING CONFIGURATION Wilbur E. Thomas, Wayne, N.J., assignor to General Binding Corporation, Northbrook, 111., a corporation of Delaware Filed Nov. 29, 1967, Ser. No. 686,633 Int. Cl. B26f 1/14 US. Cl. 83-685 Claims ABSTRACT OF THE DISCLOSURE A punching tool for stacks of sheets of paper having a rectangular cross section body member, and an integral tip having a central cutting projection.

FIELD OF THE INVENTION This invention pertains to improvements in punching configuration and more particularly relates to an improved form of cutting configuration for a punching tool to be used in a hand or a power punching apparatus.

PRIOR ART It is known to use a rectangular punching tool in a hand or power sheet punch apparatus, singly or ganged. When used in ganged form, the rectangular holes are punched in a series to permit the punched sheet material to be impaled on loose leaf binding elements. Such punches are generally formed with a long body having a rectangular cross section that corresponds to the size of hole desired to be punched.

The current shape of the sheet-engaging tips of punching tools in both hand and power punches is one having a pair of projections running along opposite sides of the rectangular cross section having a concave section therebetween with depths of up to .040 inch. Such a punch is capable of punching a thickness of .160 inch to which the dimension of the punch throat or entrance is accordingly limited. Generally it is used with a lesser thickness due to the poor quality achieved from, and the high effort level required for, full throat punching.

Such a punch when used with a 22 sheet (.003 inch each) lift, punches with ease, but the mid 25% of the lift (5-6) sheets will be torn rather than cut. As the lift thickness increases to a full throat thickness, the mid-lift situation deteriorates.

SUMMARY In accordance with the present invention, I have provided a punching tool having a rectangular cross section, and an integral tip having a central projection specially adapted to punch full throat stacks of sheet material.

A principal object of the invention is to provide a punching tool which improves the punching ability of hand and power punch apparatus.

A further object of the invention is to provide a punching tool for stacks of sheet material which punches uniform holes.

Still another object of the invention is to provide an improved punch capable of punching thick lifts of stacked sheet material and produce relatively uniform holes.

Many other advantages, features and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description and the accompanying sheet of drawings in which a preferred structural embodiment incorporating the principles of the present invention is shown by way of illustrative example.

DESCRIPTION OF THE DRAWINGS On the drawings:

ice

FIG. 1 is a view with certain parts broken away and certain other parts shown in section of a punching apparatus suitable for use with the punching tool of the invention;

FIGS. 2 and 3 illustrate the punching configuration of the invention for use in the apparatus of FIG. 1;

FIGS. 4 and 5 are enlarged partial views of the end and side of the prior art punch configuration showing the P;

FIGS. 6 and 7 illustrate a second prior art form of punch configuration; and

FIGS. 8 and 9 illustrate a third prior art form of punch configuration.

As shown on the drawings, the principles of this invention are particularly useful when embodied in a punch configuration to be used in a punching machine of the type as illustrated in FIG. 1, generally indicated by the numeral 10. This is a partial view of a power punch constructed to use the special punch configuration. Certain of the parts are not illustrated for clarity, certain others broken away and still others shown in section. The machine itself forms no part of this invention and is disclosed in US. Patent No. 3,153,966, patented Oct. 27, 1964.

The power punch 10 has a guide plate 13 mounted on and extending in advance of a pressure bar 15, and with the pressure bar 15 forming a guide means for a set pin 16, positionable to register with individual punches or punching tools 17. Normally there are a plurality of tools 17 corresponding to the number of holes to be punched operable in a selected pattern.

The machine 10 includes a die plate 43 upon which the sheets to be punched are placed and moved into engagement with a back gauge 20 adjustable to vary the positions of the punched holes from the back of the stack of sheets as desired.

The back gauge 20 is pivotally mounted at its opposite ends on two spaced bell cranks 21 vertically pivoted on the plate 43 rearwardly of the pressure bar 15 on levers 24 attached by screws 23. The bell cranks 21 are rocked to adjust the position of the back gauge 20 by means of a lever 26 attached to the pivots 24. The lever 26 has a forked upper end portion 27 extending along opposite sides of an eccentric 29, rotatable by a knob or the like (not shown) to adjust the position of the back gauge 20, in an obvious manner.

The pressure bar 15 is rigidly secured adjacent its opposite ends to a pair of rocking arms 30, extending transversely of the main frame and pivotally mounted adjacent their rear ends. The pressure bar 15 and rocking arms 30 are supported on drive links pivotally connected to the rocking arms 30 intermediate the ends thereof on pivot shafts (not shown).

The punching tools 17 are rectangular in form to punch rectangular holes in a stack of sheets, which are to be impaled on the rectangular fingers of a plastic binding element. The punch 17 is slidably supported in an upper guide plate 39 and a downwardly spaced stripper plate 40 for cooperation with a die aperture 41 in the plate 43. The aperture 41 is slightly larger than the rectangular cross section of the punch 17.

The punches 17 are positively stripped from the stack of sheets by stripper arms 45 secured to the back of the pressure bar 15 and depending therefrom and extending under a stripper bar 46 abutting at its upper side the individual pins 52 extending through the punches 17. Compression springs 49 are interposed between upper side of the stripper plate 40 and the under side of the stripper bar 46 and encircle the punch 17, to bias the stripper bar 46 into engagement with the pins 52 and to thereby effect positive raising movement of the punch 17 by operation of the stripper arm 45, upon upward movement of the pressure bar 15.

Lower end portions of leaf springs 51 extend within slots 55 formed in the set pins 16. The leaf spring 51 is moved past a dead center position when the set pin 16 is in its inwardly extended effective position and thereby holds the set pin 16 in its efiective and ineffective (shown) positions during oscillatory movement of the pressure bar 15, and enable the punching pattern to be selected at the will of the operator without removing the set pins 16 from the pressure bar 15.

The drive means for pivoting rocking arms 30 and moving the pressure bar 15 up and down, may be an electric motor (not shown).

As the rocking arms 30 are moved downwardly to effect the punching operation, one rocking arm 30 comes into engagement with the switch 112, to close said switch and complete an energizing circuit (not shown) to thereby prevent continued reciprocation of the pressure bar 15 and operation of the punches 17 in cases where the punches may once be operated and the operating switch remain actuated.

FIGS. 2 and 3 illustrate the preferred punching configuration 17 for use in the apparatus of FIG. 1. The punching tool 17 has a rectangular cross section and transverse pin 52 for engagement by the stripping bar 46. At the opposite end is a cutting tip or projection 54. The tip 54 is formed centrally of the long dimension of of the rectangular cross section. The projection extends .015 to .020 from the body and is joined thereto by a plane 56 which is at an oblique angle to the longitudinal axis of the punching tool 17.

The tool 17 provides a clean hole up to a full throat lift. It has punched up to .250 inch with paper clamped and still produces relatively clean holes. It appears to enter thick lifts without much protest. It is especially suited to punch thick lifts clean and very heavy lifts without excessive energy requirements.

The punch 60 is a prior art punching configuration. The punch 60 has two projections 62, 63 with radial segment 64 having a depth of .040 inch, FIGS. 4 and 5.

The second form of prior art punching tool 65 is shown in FIGS. 6 and 7. The punch 66 has a tip having two projecting edges 66, 67 separated by a radial segment 68 having a depth of .020 inch. It provides less raggedness than the device of FIGS. 4 and 5.

A further prior art form of punching tool 70 is shown in FIGS. 8 and 9, and corresponds to the punching tool 65. The tip is formed with a pair of projections 72, 73 separated by a radial segment 74 having a depth of .020 inch. The projection 72 extends below the projections 73 and enters the lift first.

The punch 65 is adapted to permit an increase in lift thickness of 30%, 26 to 27 sheets, with the mid-lift raggedness remaining at to 6 sheets. The punch 65 is a drastic improvement over the conventional shape punch 4 which has a depth 64 of .040 inch. The punch has the advantage of being capable of use in both hand punches and power punch equipment, FIG. 1. Full throat, .160 inch, punching is still possible but mid-raggedness is still pronounced though proportionally better than the conventional punch.

All of the current shapes of punches in both hand and powered punches are thus deficient. They will handle a thin, 20 to 22 sheet (.003 inch each) lift with ease but the mid-twenty-five percent of the lift (5 to 6) sheets will be torn rather than cut. As the lift thickness increases to a full throat condition, the mid-lift situation worsens very rapidly.

Summarizing, the single projection 54 of the punching tool 17 is specially adapted to punch uniform holes in full throat stacks of sheet material and with less effort than previously required by the prior art tools 60, 65 and 70.

I claim as my invention:

1. A tool for punching a rectangular aperture in a stack of sheet paper material or the like, said tool having a rectangular cross-section slightly smaller than and of substantially the same cross-section as a mating punching die for cutting action around the entire periphery of said die, and having a projecting tip, said tip having a central cutting projection parallel to one side of the rectangular cross-section.

2. A punching tool as recited in claim 1 wherein said projection is formed centrally of said long sides of the rectangular cross-section.

3. A punching tool as recited in claim 1 wherein the projection extends .015 to .020 inch.

4. A punching tool as recited in claim 1 wherein said cutting projection and the sides of the rectangular crosssection are joined by a plane which is at an oblique angle to the longitudinal axis of the tool.

5. A punching tool as recited in claim 2 wherein said cutting projection and the sides of the rectangular crosssection are joined by a plane which is at an oblique angle to the longitudinal axis of the tool.

References Cited UNITED STATES PATENTS 363,917 5/1887 Snyder 83-690 X 858,703 7/1907 Castle 83-694 1,411,774 4/1912 Engle -83695 1,854,516 4/1932 Kirchner 83-689 X 3,247,747 4/1966 Robbins 83660 X FOREIGN PATENTS 369,747 3/ 1932 Great Britain.

JAMES M. MEISTER, Primary Examiner US. Cl. X.R. 83689 

